This invention relates to food ingredients, to methods for the preparation of such food ingredients and to food products comprising such ingredients. The invention is particularly, but not exclusively, concerned with food ingredients for use in reduced-fat foods, and with the use of dairy whey protein in the preparation of such reduced-fat foods.
Whey is the co-product from the manufacture of dairy products which utilise the casein proteins of milk. It contains principally lactose, minerals and the whey proteins representing approximately 20% of the total protein of cows"" milk. The whey proteins are represented in majority by the two proteins, xcex1-lactalbumin and xcex2-lactoglobulin. In a previous invention a process was described for the fractionation of these major whey proteins in Australian Patent No. 616,411.
International Patent Application No. WO93/00832 (PCr/AU92/00331) (the full disclosure of which is hereby incorporated herein) describes gelled food products in which microparticulate suspensions are stabilised in heat-set gels for food applications. When restricted protein unfolding occurs as a result of heating certain globular proteins in solution, gelation may occur if specific interactions between protein molecules enable an ordered three-dimensional network to be formed. Such interactions affect intermolecular cross-lining involving hydrogen bonding, ionic and hydrophobic interactions. Adjuncts to such interacting protein systems which affect some or all of such cross-linking mechanisms may serve to modify the overall structure, texture and rheological problems of the gelled product.
Of the milk proteins. only certain of the whey proteins are capable of heat-induced gelation, xcex2-lactoglobulin is considered to be the most important whey protein for gelation since it is capable of forming uniform gels of high strength. Application of the whey protein fractionation technology developed by Pearce, yields a product which is highly enriched in xcex2-lactoglobulin and referred to as xe2x80x9cxcex2-Fractionxe2x80x9d. This product also displays the capability of forming uniform gels of high strength. (see Pearce, R. J. (1991) Applications of cheese whey protein fractions. Food Research Quarterly 51; 74-91.)
Stading and Hermnansson have described the structure and appearance of xcex2-lactoglobulin gels over a range of pH values and have described the clear gels formed below pH 4.0 and above about pH 6.5 as fine-stranded gels and the more turbid gels formed at intermediate pH as aggregate gels. The fine stranded gels formed at low pH were brittle but in the higher pH range were rubber-like. (see Stading, M. and Hermansson. A. M. (1991) Large deformation properties of xcex2-lactoglobulin gel structures. Food Hydrocolloids 5: 339-352.) The ability to form heat-set gels from food proteins is not limited to xcex2-lactoglobulin or to whey proteins. For example, heat set gelation of egg white protein is well known. Variation in the appearance and texture of such egg white gels may be achieved by manipulation of the ionic strength and pH as has been described by Hegg, P. O. (1982) Conditions for the formation of heat-induced gels of some globular food proteins. Journal of Food Science 47, 1241-1244. in a manner similar to that shown for xcex2-lactoglobulin by Stading, M and Hermansson, A-M. (1993) Large deformation properties of xcex2-lactoglobulin gels. Food Hydrocolloids 5, 339-352.
By combining the results, described in International Patent Application No. WO93/00832 with the results of Stading et al., we identified novel gelled food products in which the appearance and texture of the gelled product could be varied from clear to opaque and from elastic to inelastic according to the environmental conditions of the protein during the heat-gelation process. The resulting products demonstrated rheological characteristics of potential value in the formulation of novel foods. However, under textural analysis, these products, whether essentially elastic or inelastic. showed distinct yield points (gel breaking points). This property was considered undesirable for certain food applications.
We have now found that incorporation of a polysaccharide hydrocolloid into a heat-gelled protein results in a gelled material having a modified structure and texture which, rheologically does not display a distinct fracture point (gel breaking point). In this behavior, the gelled product exhibits the textural and Theological properties of a fat (exemplified herein by a texture profile of lard, see FIG. 13) and enables the material to be utilized as a food ingredient, e.g., a texture modifier, in food products, and especially as an ingredient in reduced-fat foods.